1. Field of the Invention
The invention relates to a lens-fitted film unit in which data on exposure is written in an IC memory whenever an exposure is, made and to a method of writing data on an exposure including an exposure date in an IC memory whenever an exposure is made.
2. Description of Related Art
Lens-fitted film units having been on the market which do not have the necessity for loading a film nor winding/rewinding the film after every exposure make one easily enjoy taking pictures. Such a lens-fitted film unit comprises a unit body with a simple exposure mechanism including a shutter installed therein and a film cartridge with a roll of unexposed filmstrip factory pre-loaded in the unit body. The unexposed filmstrip is unwound out from the film cartridge and wound into a film chamber after every exposure. When the maximum number of exposures available on the filmstrip are exposed and the filmstrip is completely wound up into the film chamber, the lens-fitted film unit is given to a photofinisher who first removes the film cartridge from the unit body to develop the negatives and makes an index print including all pictures and, if requested, individual regular prints from the negatives. On the other hand, the lens-fitted film unit without film cartridge is forwarded to the manufacturer for recycling. The developed filmstrip is reloaded in the film cartridge and returned together with the index print and regular prints to the customer. In recent years, one type of such lens-fitted film unit has an IC memory and write control IC means installed to either one of the unit body and the film cartridge for writing exposure data including a date of exposure whenever an exposure is made. As known from, for example, Japanese Unexamined Patent Publication No.9-204016 which describes a lens-fitted film unit of this kind, the exposure data are read out from the IC memory and used, for example, to print a date on a print or to make a panoramic print.
One type of lens-fitted film unit is equipped with a built-in electric flash unit. In this type of lens-fitted film unit has the necessity of having charged a capacitor of the electric flash unit to a prescribed charging voltage before making a flash exposure, which requires a charge switch which is turned on to charge the capacitor. In the case where the charge switch is of a slide type, in order to draw photographer""s attention to turning off the charge switch, the charge switch is designed and adapted such that the charge switch at its external end is situated outside the exterior surface of the unit body when it is turned on. A lens fitted film unit of this type which is known from, for example, Japanese Unexamined Patent Publication No. 7-122389 is equipped with an electric flash unit which continuously charges the capacitor even when the charge switch is turned off after it has been turned on once and spontaneously interrupts charging the capacitor when having charged the capacitor to a prescribed charging voltage.
At the manufacturer, after loading the film cartridge in the unit body to complete a lens-fitted film unit, the write control IC means of the lens-fitted film unit is connected to an external computer by the aid of which the IC memory is initialized and base data including an initial date and time (year, month, day, hour, minute and second), the maximum number of exposures available on the filmstrip and an identification (ID) number of the lens-fitted film unit are written into the IC memory. When resetting the write control IC means through the computer, the write control IC means reads out the data on an initial date and time from the IC memory and sets the data on the initial date and time in a timer circuit which counts time from the initial time as a starting time and outputs data on a cumulative time indicating a lapse of time since the initial time. The write control IC means writes the cumulative time data in the IC memory in synchronism with an appearance of a signal generated whenever a synchronous switch is closed by a shutter blade actuated to make a flash exposure. During making prints, the data on these initial date and time and cumulative time for each exposure are read out from the IC memory and then added to each other as data on a date and time of the exposure which is used to print a date on a print.
The synchronous switch possibly fails in operation at rear intervals even when the shutter blade is actually operated with the result of causing a failure in writing data in the IC memory. If, after an occurrence of a failure in writing data on an instant exposure in the IC memory, it comes out successful to write data on another exposure in the IC memory, the data written in the IC memory is processed as data for the instant exposure. That is, there occurs inconsistency between a number of exposure and data on the exposure. This inconsistency causes an error that a wrong exposure date is printed on a print.
In the case where the electric flash unit is not of the type that spontaneously interrupts charging the capacitor, a built-in battery loses power as low as insufficient to charge the capacitor to the prescribed charging voltage in approximately five hours if a slide type charge switch is imprudently left turned on. Even in the case where the electric flash unit is of the type that spontaneously interrupts charging the capacitor, the built-in battery loses its power in approximately 100 hours if the slide type charge switch is imprudently left turned on. In either case, if the built-in battery exhausts its power before the maximum number of exposures available on the filmstrip have been exposed, it is impossible to write data on exposures in the IC memory.
When writing an initial date and time with the precision of a second or seconds in the IC memory, counting time with the precision of a second or seconds and writing a cumulative time with the precision of a second or seconds in the IC memory, the date and time printed on a print is accurate. However, if the lens-fitted film unit is left unused for a long period of time, the amount of data on a cumulative time becomes too large to be written in the IC memory. While this problem can be overcome by installing an IC memory having a large memory capacity, it causes an increase in cost of the lens-fitted film unit. Thereupon, when writing or counting the initial time, a lapsed time and a cumulative time with the precision of an hour, while the IC memory may have a small memory capacity, however, the date of exposure is possibly inaccurate because the cumulative time has an error of xc2x11 hour.
It is therefore an object of the invention to provide a lens-fitted film unit equipped with a built-in electric flash unit which certainly writes data on exposures in the IC memory even when a synchronous switch for causing the electric flash unit to make a flash fails in operation so as thereby to prevent an occurrence of inconsistency between an exposure and data on the exposure.
It is another object of the invention to a lens-fitted film unit equipped with a built-in electric flash unit which causes only a small loss in battery power even while a charge switch is imprudently left turned on and makes it reliable to write data on exposures in the IC memory.
It is a further object of the invention of the invention to provide a method of writing data on an exposure date which provides improved accuracy of an exposure date written in an IC memory and saves a memory capacity of the IC memory assigned to exposure dates.
According to one aspect of the invention, a lens-fitted film unit equipped with an exposure mechanism and a built-in electric flash unit comprises a film cartridge pre-loaded in the lens-fitted film unit, an IC memory installed to either one of the lens-fitted film unit and the film cartridge in which exposure data is written and write control IC means for controlling writing the exposure data in the IC memory, and switch means for causing the write control IC means to write the exposure data in the IC memory when actuated or turned on by the exposure mechanism during making an exposure. The switch means comprises a synchronizing switch which is actuated or turned on by a shutter blade of the exposure mechanism to cause the built-in electric flash unit to make a flash and an auxiliary switch which is actuated or turned on by operation of the shutter mechanism. The write control IC means is actuated to control or perform writing the exposure data in the IC memory when at least either one of the synchronizing switch and the auxiliary switch is actuated. In its simplest form, the auxiliary switch may be actuated by the shutter blade of the exposure mechanism during making an exposure.
In this embodiment, the construction of the switch means that actuation of at lest either one of the synchronizing switch and the auxiliary switch causes writing exposure data in the IC memory provides certainty of writing exposure data in the IC memory even if the synchronizing switch fails in operation for some reasons or other, which prevents an occurrence of inconsistency between an exposure and data on the exposure. The auxiliary switch constructed to be actuated by the shutter blade provides mechanical simplicity while providing certainty of writing exposure data in the IC memory.
In another aspect of the invention, the built-in electric flash unit has a charge switch which is actuated or turned on to charge a capacitor of the built-in electric flash unit and remains turned on until turned off, and the IC means has a charge control terminal which is connected to the built-in electric flash unit and changeable between an interruption state in which charging the built-in electric flash unit is interrupted and a permission state in which charging the built-in electric flash unit is permitted. The charge control terminal is turned into the interruption state immediately after an exposure to write data of the exposure in the IC memory during interruption of charging the built-in electric flash unit. The charge control terminal is turned into the interruption state at a lapse of a specified time which is counted by a timer of the IC means, which is actuated in response to actuation of the charge switch, while the charge switch remains turned on.
According to the embodiment, charging the built-in electric flash unit is interrupted by turning the charge control terminal of the IC means into the interruption state when a specified time lapses while the charge switch is left turned on, which makes a lose of battery power as small as possible even while the charge switch is imprudently or accidentally left turned on and guarantees to write exposure data whenever an exposure is made. The charge switch may be of a slide type which provides mechanical simplicity and makes a reduction in cost of the lens-fitted film unit.
In another aspect of the invention, the method of writing data on an exposure date in the IC memory installed to either one of a lens-fitted film unit with an exposure mechanism and a film cartridge pre-loaded in the lens-fitted film unit comprises the steps of writing data on an initial date and time as a starting time with the precision of a second or seconds in the IC memory at shipping of the lens-fitted film unit, counting a cumulative time from the starting time with the precision of a second or seconds, and writing data on the cumulative time since the starting time with the precision of an hour in the IC memory whenever an exposure is made.
Performing both writing initial date and time and counting time with the precision of a second or seconds provides improved accuracy of an exposure date and prevents an error of xc2x11 hour which is possibly caused in the case where counting time with the precision of an hour with discarding minutes and seconds. Further, the capacity of the IC memory assigned to exposure dates is saved.